Based on the signs, I would recommend "CR-B15" as the format. There's no hyphen, and the sign says "County", and doesn't say "Highway". I think that's plenty clear enough.

TTS should say "County Road B Fifteen" for that.

Exits that share a milepost are designated with numbers, e.g., "Exit 235B". In my area, that's how they are displayed on the big green signs, and that's how they are on the Waze map as well: "Exit 235B: Canal St / Superdome". It is pronounced properly, as you might expect, "Exit Two Thirty-Five B, Canal Street, Superdome". I imagine it would work the same with the letter before the number, then.

Not sure about "PA-1", but I know that "LA-1" is prononuced as "L A One". As for the other letters, none of them stand for anything. Michigan smartly skips from D to F in their county road designations and stops before N, so we don't have to worry about any cardinal directions slipping into there.

robc007 wrote:I drove through Pellston this week and was able to extend some of the county routes for you.

Unless I'm mistaken, county routes are generally "Primary Street" and the state routes are generally "Minor Highway".

My impression is that the US routes should also be "Minor Highway" unless they are divided and limited access, etc. However, someone has made all of the US routes in northern Michigan into "Major Highway". This is something that I would like to make more consistent with southern Michigan, but my editing area isn't large enough to make any of those changes.

That was originally how we did it here in Louisiana, but since there is no real functional difference between major and minor highways, we decided to make US highways Major and Louisiana highways Minor, essentially for display purposes. These are minimums, so a more important state highway can be Major and, of course, a freeway in either system can be Freeway.

In general, rural routes should be set at a higher level than equivalent routes in built-up areas. Even though they're typically narrow, they still carry high-speed traffic, and are still used for medium- to long-distance routing.

Based on the standards set forth in the Wiki, the Primary Street type is only used for edit intra-city travel; any route used for inter-city travel should be a Minor Highway or higher. "Main Street" small towns, which typically sit along or at the intersection of inter-city routes, won't typically have any Primary Street class routes at all, below a certain size, perhaps unless they are accessed by small collector roads off a main route. I don't think that's very common with Southeast Michigan's grid system, though.

So basically, if a county highway connects towns, it should probably be a Minor Highway. If it's a smaller main road that only serves a town or possibly two towns in close proximity, Primary Street could do.

And since there are necessarily going to be sort of a lot of highways, making all US routes Major Highway is a good way to distinguish them.

Oh, sure, don't hesitate to upgrade certain local roads to "primary street" if it makes sense to do so. That's pretty much a judgment call. Last I looked, Detroit is in pretty bad shape with respect to Primary Streets.